A trendy wholefoods store has been slammed for the 'extraordinarily heartless' dismissal of a chef who took time off to receive cancer treatment.

Chanintorn Siri was fired from Urban Orchard Food in Sydney's Circular Quay after he took three days' sick leave to be treated for severe stomach pains related to his pancreatic cancer.

His boss Gabrielle Levette called him two days into his hospital stay to tell him he no longer worked at the store, saying he was an unreliable employee.

Ms Levette told the Fair Work Commission that Mr Siri often fraudulently filled out his timesheet, once closed the store too early, took regular sick leave for 'no reason' and was often late for shifts.

Chanintorn Siri was fired from Urban Orchard Food (pictured) in Sydney's Circular Quay after he took three days' sick leave to be treated for severe stomach pains related to his pancreatic cancer

The commission ruled in favour of Mr Siri, saying he had been unfairly sacked.

'Although the applicant may have exhibited some level of what might be described as less than perfect work performance, conduct and capacity, these were not matters that jeopardised the ongoing employment,' commissioner Ian Cambridge said.

'The employer acted with callous and undue haste when it engaged a replacement employee.'